3D-printed tooling and methods for producing same

ABSTRACT

Techniques for 3-D printing a tooling shell for use in producing panels for a transport structure, such as an automobile, boat, aircraft, or other vehicle, or other mechanical structure, are disclosed. A 3-D printer may be used to produce a tooling shell containing Invar and/or some other material for use in molding the panels. A channel may be formed in a 3-D printed tooling shell for enabling resin infusion, vacuum generation or heat transfer. Alternatively, or in addition to, one or more hollow sections may be formed within the 3-D printed tooling shell for reducing a weight of the shell.

BACKGROUND Field

The present disclosure relates generally to tooling techniques inmanufacturing, and more specifically to 3-D printed tooling for use inproducing panels in vehicles, boats, aircraft and other mechanicalstructures.

Background

Numerous types of panels are widely manufactured and used in transportstructures such as vehicles, trucks, trains, motorcycles, boats,aircraft, and the like. Panels may be internal to the body of thestructure, such as, for example, interior door panels within a vehicle.Panels may also include exterior body panels assembled as part of avehicle's chassis. Among other functions, such exterior panels definethe external shape and structure of the vehicle and are viewable by anobserver outside the vehicle.

There too, a wide variety of materials are used in the manufacture ofsuch panels. The choice of materials typically depends on the purpose,function, and intended use of the panel. Recently, manufacturers havepaid particular attention to using materials that can minimize theweight of vehicles to increase fuel efficiency. Strength, durability,longevity and aesthetic appearance are other factors contributing to theselection of such materials for use in panels. For example, interiorpanels may be composed of molded plastic, metal, fiberglass, and wood,among other materials. Exterior panels constituting a transportstructure's frame, by contrast, may require more specialized materialsdesigned to address existing safety specifications.

A particular focus of attention in recent years has been the use ofcomposite materials for creating panels. Generally, a composite materialis formed from two or more different materials that are combinedtogether to create specific properties that are superior to the originalproperties of the individual materials. Composite materials such asfiberglass and carbon fiber are used in the manufacture of compositepanels used in transport structures.

Carbon fiber is a common material used in the formation of numerous,high-performance structures requiring stiffness, strength and durabilitywithout the heavy weight often associated with alternative candidatematerials. Carbon Fiber Reinforced Polymer (CFRP) is an extremely strongand lightweight fiber-reinforced plastic. As the name suggests, CFRPincludes materials formed using a combination of carbon fibers and apolymer-based resin (or other binding agent) to form a new compositematerial with durable properties that exceed its constituent materials.Due to its strength and lightweight nature, CFRP is frequently used inthe manufacture of body panels and other components for vehicles, boats,motorcycles, aircraft, and other mechanized assemblies, in addition tohaving numerous other industrial and commercial applications.

Challenges that have arisen in recent years include determining moreefficient, environmentally-friendly, faster, and less costly techniquesfor producing panels using composite materials. In conventionalproduction techniques, a tool for molding the composite material istypically manufactured using labor-intensive processes. For example, amachining process may be used to manufacture a pair of tooling shellswhich may each constitute one of a positive and a negative section of amold. Materials and resin may be placed in the mold between the positiveand negative tooling shell sections to thereby shape a panelconstituting the target composite material. The tooling shells, in turn,are typically composed of one or more materials that are chemically andstructurally suitable for use in molding the subject materials.

Suitable candidate materials for the tooling shells include those thatcan withstand the pressures associated with molding and that havethermal characteristics compatible with a given composite material.Unfortunately, many such candidate materials are difficult and costly tomachine into tooling shells using traditional methods. These lattermethods often involve the time-consuming and laborious process ofshaping an expensive block of material having tough or ductileproperties or other undesirable characteristics not conducive to themachining process. As an illustration, some otherwise desirablematerials may be soft and gummy, making them difficult to accuratelycut. This renders tasks like carving the material and formulatingdetailed structure therein a particular manufacturing challenge. Forthese and other reasons, labor-intensive machining techniques can resultin complex and costly obstacles to manufacturers. They can also imposesignificant practical limitations on the allowable shape, size andgeometrical complexity of the resulting tooling shell such that, forexample, it may be difficult or impractical to construct certain desiredfeatures or to streamline an optimal shape of the shell. The resultingtooling shell may be bulky and unwieldy, imposing additional burdens onpersons working with the materials to mold panels. Alternativemanufacturing processes used to overcome these issues include castingthe main tooling and then machining the mold surface. However thissolution is costly and time consuming, and therefore not suitable forlow to medium volume production.

These and other shortcomings are addressed in the present disclosure.

SUMMARY

Several aspects of tooling shells and methods for producing toolingshells will be described more fully hereinafter with reference tothree-dimensional printing techniques.

One aspect of a method of three-dimensional (3-D) printing a toolingshell suitable for producing a composite panel for a transport structureincludes receiving instructions for printing the tooling shell, theinstructions based on a data model of the tooling shell, receivingmaterial comprising Invar, and printing the tooling shell based on theinstructions using the material.

Another aspect of a method of three-dimensional (3-D) printing a toolingshell suitable for producing a panel for a transport structure includesreceiving instructions for printing the tooling shell, the instructionsbased on a data model of the tooling shell, receiving material, andprinting the tooling shell based on the instructions using the material,wherein the printing the tooling shell comprises forming a hollowsection in the tooling shell.

An aspect of an apparatus suitable for producing a composite panel for atransport or other mechanical structure includes a three-dimensional(3-D) printed tooling shell comprising Invar.

Another aspect of an apparatus suitable for producing a panel for atransport or other mechanical structure, the apparatus comprising athree-dimensional (3-D) printed tooling shell comprising a channel toenable resin infusion, vacuum generation, or heat transfer.

Another apparatus suitable for producing a panel for a transportstructure includes a three-dimensional (3-D) printed tooling shellcomprising a hollow section formed therein.

An aspect of a method of three-dimensional (3-D) printing a toolingshell suitable for producing a composite panel for a transport or othermechanical structure includes receiving instructions for printing thetooling shell, the instructions based on a data model of the toolingshell, receiving material comprising an alloy configured to includethermal characteristics and a stiffness suitable for molding thecomposite panel using the tooling shell, and printing the tooling shellbased on the instructions using the material.

It will be understood that other aspects of tooling shells and methodsof producing tooling shells will become readily apparent to thoseskilled in the art from the following detailed description, wherein itis shown and described only several embodiments by way of illustration.As will be realized by those skilled in the art, the tooling shells andmethods for producing tooling shells are capable of other and differentembodiments and its several details are capable of modification invarious other respects, all without departing from the invention.Accordingly, the drawings and detailed description are to be regarded asillustrative in nature and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of tooling shells and methods for producing toolingshells will now be presented in the detailed description by way ofexample, and not by way of limitation, in the accompanying drawings,wherein:

FIG. 1 is a flow diagram illustrating an exemplary process of initiatinga process of 3-D printing.

FIG. 2 is a block diagram of an exemplary 3-D printer.

FIGS. 3A-D are diagrams illustrating side views of an exemplary paneland exemplary 3D-printed tooling shells, and various stages of a processfor using a 3D-printed tooling shell for producing the panel.

FIGS. 4A-B are a flow diagram illustrating an exemplary process forproducing a 3D-printed tooling shell used for producing a panel for usein a transport structure.

FIG. 5 is a cross-sectional view of an exemplary 3-D printed toolingshell incorporating hollow structures and integrated channels.

FIG. 6 is a flow diagram illustrating an exemplary process for producinga 3D-printed tooling shell incorporating hollow structures andintegrated channels.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings is intended to provide a description of various exemplaryembodiments of tooling shells and method of producing tolling shells andis not intended to represent the only embodiments in which the inventionmay be practiced. The term “exemplary” used throughout this disclosuremeans “serving as an example, instance, or illustration,” and should notnecessarily be construed as preferred or advantageous over otherembodiments presented in this disclosure. The detailed descriptionincludes specific details for the purpose of providing a thorough andcomplete disclosure that fully conveys the scope of the invention tothose skilled in the art. However, the invention may be practicedwithout these specific details. In some instances, well-known structuresand components may be shown in block diagram form, or omitted entirely,in order to avoid obscuring the various concepts presented throughoutthis disclosure.

The use of 3-D printing in the context of composite tooling providessignificant flexibility for enabling manufacturers of mechanicalstructures and mechanized assemblies to manufacture parts with complexgeometries. For example, 3-D printing techniques provide manufacturerswith the flexibility to design and build parts having intricate internallattice structures and/or profiles that are not possible to manufacturevia traditional manufacturing processes.

FIG. 1 is a flow diagram 100 illustrating an exemplary process ofinitiating a process of 3-D printing. A data model of the desired 3-Dobject to be printed is rendered (step 110). A data model is a virtualdesign of the 3-D object. Thus, the data model may reflect thegeometrical and structural features of the 3-D object, as well as itsmaterial composition. The data model may be created using a variety ofmethods, including 3D scanning, 3D modeling software, photogrammetrysoftware, and camera imaging.

3D scanning methods for creating the data model may also use a varietyof techniques for generating a 3-D model. These techniques may include,for example, time-of flight, volumetric scanning, structured light,modulated light, laser scanning, triangulation, and the like.

3-D modeling software, in turn, may include one of numerous commerciallyavailable 3-D modeling software applications. Data models may berendered using a suitable computer-aided design (CAD) package, forexample in an STL format. STL files are one example of a file formatassociated with commercially available CAD software. A CAD program maybe used to create the data model of the 3-D object as an STL file.Thereupon, the STL file may undergo a process whereby errors in the fileare identified and resolved.

Following error resolution, the data model can be “sliced” by a softwareapplication known as a slicer to thereby produce a set of instructionsfor 3-D printing the object, with the instructions being compatible andassociated with the particular 3-D printing technology to be utilized(step 120). Numerous slicer programs are commercially available. Slicerprograms convert the data model into a series of individual layersrepresenting thin slices (e.g., 100 microns thick) of the object beprinted, along with a file containing the printer-specific instructionsfor 3-D printing these successive individual layers to produce an actual3-D printed representation of the data model.

A common type of file used for this purpose is a G-code file, which is anumerical control programming language that includes instructions for3-D printing the object. The G-code file, or other file constituting theinstructions, is uploaded to the 3-D printer (step 130). Because thefile containing these instructions is typically configured to beoperable with a specific 3-D printing process, it will be appreciatedthat many formats of the instruction file are possible depending on the3-D printing technology used.

In addition to the printing instructions that dictate what and how anobject is to be rendered, the appropriate physical materials necessaryfor use by the 3-D printer in rendering the object are loaded into the3-D printer using any of several conventional and often printer-specificmethods (step 140). In fused deposition modelling (FDM) 3-D printers,for example, materials are often loaded as filaments on spools, whichare placed on one or more spool holders. The filaments are typically fedinto an extruder apparatus which, in operation, heats the filament intoa melted form before ejecting the material onto a build plate or othersubstrate, as further explained below. In selective laser sintering(SLS) printing and other methods, the materials may be loaded as powdersinto chambers that feed the powder to a build platform. Depending on the3-D printer, other techniques for loading printing materials may beused.

The respective data slices of the 3-D object are then printed based onthe provided instructions using the material(s) (step 150). In 3-Dprinters that use laser sintering, a laser scans a powder bed and meltsthe powder together where structure is desired, and avoids scanningareas where the sliced data indicates that nothing is to be printed.This process may be repeated thousands of times until the desiredstructure is formed, after which the printed part is removed from afabricator. In fused deposition modelling, parts are printed by applyingsuccessive layers of model and support materials to a substrate. Ingeneral, any suitable 3-D printing technology may be employed forpurposes of this disclosure.

FIG. 2 is a block diagram of an exemplary 3-D printer 200. While anynumber of 3-D printed technologies can be suitably employed, the 3-Dprinter 200 of FIG. 2 is discussed in the context of an FDM technique.3-D printer 200 includes an FDM head 210 which in turn includesextrusion nozzles 250A and 250B, a moveable build stage 220, and a buildplate 230 at the top of the build stage 220.

Depending on the intended composition of the structure and the need forany support material for providing support to overhanging elements ofthe structure that might otherwise be subject to possible gravitationaldeformation or collapse, a plurality of materials may be used forprinting an object. One or more suitable filament materials 260 may bewound on a spool (not shown) and fed into FDM head 210. (In othertechnologies described above, the material may be provided as a powderor in other forms). The FDM head 210 can be moved in X-Y directionsbased on the received printing instructions by a numerically controlledmechanism such as a stepper motor or servo motor. The material, whichmay in one exemplary embodiment constitute a thermoplastic polymer, maybe fed to the FDM head 210 which includes the extrusion nozzles 250A and250B. The extruder in FDM head 210 heats the filament material 260 intoa molten form, and extrusion nozzle 250 a ejects the molten material anddeposits it onto the build plate 230 of build stage 220.

Responsive to the received printing instructions, the FDM head 210 movesabout a horizontal (X-Y) plane such that extrusion nozzle 250A drops thematerial 260 at the target location to form a line 240 of appliedmaterial. (The FDM head 210 may also be configured to move in theZ-direction and/or to rotate about one or more axes in certainconfigurations). The layer 270 of material 260, including line 240, isformed by depositing the material 260 line by line, with each line ofthe material 260 hardening as the material is deposited on the buildplate 230. After one layer 270 is formed at the appropriate locations inthe X-Y plane, the next layer may be formed in a similar way.

The build plate 230 may be a component of a controlled table moveable inat least the vertical Z direction. When rendering of a layer 270 iscompleted, the build stage 220 and build plate 230 may lower by anamount proportional to the thickness of layer 270 in the vertical (Z)direction so that the printer can begin application of the next layer,and so on until a plurality of cross sectional layers 240 having adesired shape and composition are created.

While a substantially rectangular structure of layers is shown forpurposes of simplicity in this illustration, it will be appreciated thatthe actual printed structure may embody substantially any shape andconfiguration depending on the data model. That is, the actual shape ofthe rendered layers will correspond to the defined geometry of the3D-model being printed.

In addition, as indicated above, a plurality of different materials maybe used to print the object. In some instances, two different materials260 and 280 may concurrently be applied by respective extruder nozzles250A and 250B.

Panels for transport and other mechanical structures may be constructedfrom various composite materials that provide strong support with alightweight structure. One such material attractive for use in moldingthese panels is Invar, a nickel steel (Ni—Fe) alloy being approximately36% nickel and approximately 64% iron. Invar is used as a tooling shellin the production of composites such as CFRP and the like. Invar isknown for its low coefficient of thermal expansion (CTE) and thus itsrelative lack of expansion or contraction with temperature changes.Invar has a CTE that is relatively similar to that of Carbon FiberReinforced Polymer (CFRP). For this reason, Invar is commonly used as amold in CFRP composite tooling. The use of an Invar tool may beparticularly desirable for producing CFRP structures because asignificant CTE mismatch between the tooling material and the compositematerial can cause unwanted thermal expansion of materials. Suchexpansion can be detrimental in manufacturing high tolerance compositeparts. The use of Invar in connection with CFRP tooling reduces thephenomenon of CTE mismatch. Invar is stable and nearly immune toshrinkage or expansion due to extreme changes in temperature. Invar isconsequently desirable for use in molding CFRP and similar materials.

An exemplary table setting forth Invar's approximate CTE as a functionof its temperature is provided below.

Temperature (° F.) CTE (×10⁻⁶ ° F.⁻¹) 200 0.72 300 1.17 500 2.32 7004.22

In addition, the approximate modulus of elasticity of Invar is 20.5Mpsi. The elasticity modulus is a general measure of a material'sresistance to being deformed when a force (such as a molding force) isapplied to it. This value of the modulus of elasticity provides Invarwith a high stiffness suitable for dimensional stability of theresulting tooling shell.

In other embodiments, a method for 3-D printing tooling shell includesusing, in lieu of Invar, a different alloy that has thermal propertiesand stiffness characteristics that are suitable for molding a compositepanel including carbon fiber. Thus, for example, an alloy that includescharacteristics that are comparable to the exemplary values describedabove may be a suitable material for the 3-D printed tooling shell.

As discussed above, many materials that are otherwise suitable for useas tools in producing body panels are difficult to construct. Beingtough and ductile, Invar, for one, is notoriously difficult andexpensive to machine. The difficulty and time-consuming nature ofsculpting Invar using traditional machining techniques often results inInvar tools that are unnecessarily thick and heavy, making such toolsmore difficult for workers to handle in the molding process. Further,the machining limitations of Invar and similar materials make itdifficult or impractical to accurately integrate detailed structuralfeatures in the tooling shell that may otherwise be useful in theensuing molding process. Thus, existing Invar and similar tools lackversatility. The cost and complexity of the machining and toolingprocesses for these materials increase significantly in directproportion to the increase of part performance requirements (such as,for example, in vehicle and aircraft applications), the number of partsto be produced, the complexity of the parts, and other factors.Additionally, the excessive mass of these tools requires extendedthermal ramp-up and cool down parameters in the molding process,limiting the production cycle time and associated rate capability.

The 3-D printed tooling shell may be incorporated, for example, as asection of a mold for use in producing panels for transport and othermechanical structures. In an exemplary embodiment, the 3-D printedtooling shell includes Invar or similarly performing alloys, and is usedto mold composite body panels using a carbon fiber composite materialsuch as CFRP. Preferably the 3-D printed tooling shell is comprised ofsubstantially Invar or a similar alloy. “Substantially Invar” means thatthe 3-D printed tooling shell is comprised of pure Invar, or principallyof Invar with some minor composition of other materials (whetherintended materials or impurities) that do not materially affect the CTEor other desirable properties of the tooling shell to serve its intendedpurpose, or of an Invar like alloy that has similar mechanical and CTEcharacteristics.

FIGS. 3A-D are diagrams illustrating side views of a panel and3D-printed tooling shells, and various stages of a process for using a3D-printed tooling shell for producing the panel. FIG. 4 is a flowdiagram illustrating an exemplary process for producing a 3D-printedtooling shell used for producing a panel for use in a transportstructure. In one exemplary embodiment, the tooling shell is being usedas one of a positive or negative a mold to produce the body panel in oneof any conventional molding processes. In the embodiment shown, the bodypanel contemplated for production is composed of CFRP.

It should be understood that the tooling shells herein are not limitedto molding composite body panels, and practitioners in the art willappreciate that the disclosed tooling shells can be used in a variety ofindustrial and commercial applications.

In the paragraphs that follow, FIGS. 3 and 4 will be collectivelyreferenced, where appropriate.

Referring initially to FIG. 3A and FIG. 4, the topology optimizationphase at the concept level of the design process is described. In thisphase, the geometry and composition of a composite body panel 302 may bedesigned (step 410). That is, the panel's overall topology, its specificcomposition of materials, its geometrical and structural features, andany other desired properties or characteristics may be defined at thisstage. The material layout for the body panel may be optimized based onan understood set of loads and design constraints such that the layoutadheres to some target performance objectives. In the case ofmanufacturing an automobile, for example, this step may includeidentifying the structure, shape and features of the panel desired, andthe composition of materials necessary for producing the panel, thatallow the panel to fall within certain desired specifications (e.g.,weight requirements and safety specifications, etc.).

The specific panel assembly techniques may then be identified (step420). This step may include, for example, identification and selectionof the specific method of assembly of the panel 302 (such as anidentification of the molding and resin infusion processes to be used),selection of the layup process (such as wet versus dry layup, etc.),determination of the resin infusion process, and determination of thearchitecture and composition of the tooling shells. That is, this stepmay further include determination of the desired structures, geometriesand compositions of the tooling shells based on the above-identifiedproperties of the panel design. For example, tooling shells may havedifferent structures based on whether the tooling shell is part of apositive or negative mold section, as described further below.

It will be appreciated that in other embodiments and depending on theapplication involved, part or all of the steps 410 and 420 in FIG. 4 mayequally well occur in reverse order such that the manufacturing andassembly techniques may precede one or more of the steps involved indesigning the features of the panel.

In addition, it is generally understood that in many conventionalmolding techniques, at least two tooling shells are used as part of amold for creating a part. For example, in an exemplary embodiment, amolding process as described herein may use a first tooling shell as apositive section of the mold and a second tooling shell as a negativesection of the mold. The positive section of the mold may ultimatelyembody the intended shape of the part, such as the external surface of abody panel on a vehicle. The construction and number of tooling shellsused herein may consequently vary depending on the specific moldingtechniques employed. It should be noted that wide variety of moldingtechniques may be employed depending on the application and potentiallyother factors such as the anticipated volume of production, etc. Forexample, in one exemplary embodiment, the use of prepregs with vacuumbagging equipment is employed. Vacuum bagging is a technique used tocreate mechanical pressure on the laminate during the cure cycle. Amongother benefits, pressurizing the composite laminate using vacuum baggingremoves trapped air, compacts the fiber layers, and reduces humidity. Inanother exemplary embodiment, autoclave molding using high temperaturesand pressures is employed. Autoclave molding is a standard compositemanufacturing procedure that provides pressure and temperature accordingto a particular thermal curing cycle. The high pressure applied usingthis technique ensures a significant void reduction inside the compositestructure. The aforementioned techniques may be suitable in certainimplementations involving low production volumes of parts.

With reference to the panel assembly techniques (step 420), which mayinclude identification of the features of the tooling shell, a suitabledata model may be constructed based on these features (step 430). Thedata model may describe the 3-D geometry and composition of the toolingshells as identified with respect to step 410. In an exemplaryembodiment, a CAD program is used to create one or more files, such asan STL file, containing the data model. In some embodiments, the datamodel generation process may overlap with one or more of the processesidentified with respect to steps 410 and 420. For example, the datamodel may be generated concurrently with the panel design.

The data model generated in step 430 may be converted via a slicerprogram or other available procedure to a set of instructions suitablefor input to a 3D printer (step 440). Generally, the structure andgeometry of the tooling shells to be rendered may be developed anddescribed in one or more electronic files and/or software programs to beused as the input of a 3-D printer, as is conventionally understood.

The 3-D printer is then loaded with the suitable printing materials, byway of example, Invar or, if desired, additional materials for use asthe model material in constructing the tooling shell along with anysupport materials required (step 450). As discussed above, the materialsmay be loaded as a spool with filament in a 3D printer, as a powder, orthrough another suitable technique specific to the 3-D printer in use.In addition, the program files generated in connection with step 440,above, are input to the 3-D printer such that the 3-D printer receivesinstructions for printing the tooling shell (step 460). It will beappreciated that the supplying of materials to the 3-D printer may occurat any suitable stage of the processes described herein and is notnecessarily limited to the order ascribed this step in FIG. 4.

Using the instructions, the 3-D printer prints a tooling shell 304 (FIG.3B, FIG. 4, step 470. For example, the 3-D printer may print the toolingshell having a complex inner lattice matrix section in the toolingshell. In general, 3-D printing may include a process of making athree-dimensional structure based on a computational or electronic modelas an input. The 3-D printer can be configured to generate the toolingshell through additive and/or subtractive manufacturing, or via anothermethod. Any suitable 3-D printing process may be used. The 3-D printermay be a direct metal laser sintering (DMLS) printer, electron beammelting (EBM) printer, fused deposition modeling (FDM) printer, aPolyjet printer, or any of the techniques described elsewhere in thisdisclosure. The 3-D printer may use extrusion deposition, granularbinding, lamination, or any other 3-D printing technology. As describedabove, the 3-D printing process may involve breaking down the design ofthe 3-D object into a series of successive digital layers or slices,which the printer will then form layer-by-layer until the renderedobject is completed. Tooling shells as described herein may havedifferent geometries and complexities and may be printed in alayer-by-layer fashion. A wide range of geometric designs and detailedinternal and external features of the tooling shell may also beaccommodated.

In addition, the 3-D printing as contemplated herein may involve complexmatrix arrays as backing structures, eliminating the need for temporarysupport material during the 3DP process, and giving reduced toolingthermal mass and lower material usage, thereby reducing manufacturingcost of the tool and lower molding process time due to reduced thermalcycle time.

The example in FIG. 3B shows a simplified geometry of a resultingtooling shell 304 that is intentionally designed to be relatively thin.In an exemplary embodiment, the tooling shell may be an Invar toolingshell, which is a tooling shell substantially composed of Invar asdefined above. Shell thickness and backing structure matrix density canbe optimized to minimize tool mass based on tool size and form so thatsufficient tool stiffness and stability during curing is met Thus, incontrast to prior techniques involving the machining of often unwieldyand unnecessarily large chunks of Invar material, 3-D printing thetooling shell (using Invar or other suitable materials) providessignificant flexibility to design and print a tool having a shape andgeometry that is generally easier to manipulate in the manufacturingprocess. Thus, one of several advantages of the 3-D printed toolingshell 304 is that, in contrast to a bulky or heavy shells that aremachined using conventional methods, the tooling shell 304 may beconstructed to be relatively thin and lightweight, saving materialcosts.

It will nonetheless be appreciated that any number of desired toolshapes and structures may be contemplated depending on the moldingprocess to be used and design requirements of the panel to be producedusing the tooling shell. The use of 3-D printing of the tooling shellalso provides the designer with significant flexibility to produceshells having very complex shapes to mold more complicated paneldesigns.

Referring still to FIG. 3B, a geometry 305 of a panel to be moldedwithin the tooling shell 304 may be designed to conform to the shape ofan inner surface of the tooling shell 304, depending on how the mold isconfigured. In this manner, the tooling shell acts as a section of amold to shape the composite material that will be cured into the panel,as described further below.

After the tooling shells are printed, they may be used to produce apanel (FIG. 4, steps 480, 490). The composite layup may be performedusing the tooling shell. FIG. 3C illustrates a second 3-D printedtooling shell 307 designed to be used in conjunction with the first 3-Dprinted tooling shell 304 as first and second sections of a mold. Inthis example, carbon fiber material 306 (or another suitable material)may be applied via a layup process on the back or outer surface of thetooling shell 307 as a first step in producing a panel. The carbon fibermaterial 306 may be laid over the tooling shell 307. (In otherembodiments, the material 306 may alternately or additionally be appliedover an inner surface of tooling shell 304).

In one exemplary embodiment, a layup uses pre-impregnated (“prepreg”)carbon fiber plies that are delivered onto the tooling shell 307 withthe resin matrix applied. The prepreg technique provides effective resinpenetration and assists in ensuring substantially uniform dispersion ofthe resin. The prepreg plies may be applied onto the tooling shell 307to form a laminate stack.

In another embodiment, a dry lay-up uses dry woven fiber sheets. Resinmay thereupon be applied to the dry plies after layup is complete, suchas by resin infusion. In an alternative exemplary embodiment, wet layupmay be used wherein each ply may be coated with resin and compactedafter being placed.

FIG. 3D shows a mold 308. Where Invar is used, the Invar tooling shell304 is applied over the Invar tooling shell 307 as positive and negativesections in a mold to shape the carbon fiber material into the form ofthe body panel 302 (step 490). Upon completion of the molding process,the carbon fiber material may, for example, be vacuum compacted andbaked in an oven for a designated time period.

The specific molding and resin infusion processes used during thesestages may vary depending on variables such as molding techniques,design constraints, and desired manufacturing yield. Generally, the3-D-printed tooling shell may be used in connection with a variety ofcomposite manufacturing techniques including, for example, ResinTransfer Molding (RTM), hand layup, prepregs, sheet molding, and VacuumAssisted Resin Transfer Molding (VARTM).

For example, with reference to the mold 308 of FIG. 3D following carbonfiber layup, clamps may be affixed on respective left and right sides ofthe mold 308 to press tooling shells 304 and 307 together. One of thetooling shells may include a channel (as described below) through whichlow viscosity resin and an appropriate catalyst can flow via a resininjector. Temperature control may also be maintained via one or moreheating channels.

The use of the above-described techniques to produce the tooling shells304 and 307 may be suitable in some implementations for manufacturingapproximately 1-500 composite body panels. In other instances, thesetechniques may be employed to produce more than 500 parts, whether aloneor using a platen press or other method. Among other benefits, thetooling technique according to these aspects accords manufacturers withsignificant flexibility to produce both tooling shells and compositepanels having varying geometries and complexities.

As an illustration of this flexibility, tooling shells may be 3-Dprinted incorporating one or more hollow sections. The use of definedhollow sections in the tooling shells achieved via 3-D-printing mayresult in considerable weight savings for the tooling. In addition todecreased costs as a result of saving material and reduced time for3-D-printing, the tooling shells constructed as described herein may bemade easier and less wieldy for use in the panel tooling process.

In another exemplary embodiment, the tooling shells are 3-D-printed withintegrated channel structures. Various channels may be used inconnection with the manufacturing processes of composite panels andother structures. These channels may, for example, include heating orcooling channels, channels for resin infusion, channels for vacuumgeneration, and the like. The channels can easily be integrated into thetooling shells themselves via 3-D printing techniques. In addition toproviding great flexibility, these techniques may save the manufacturerconsiderable time and expense with respect to the machining processes ofInvar and other materials used in such tooling shells.

FIG. 5 is an exemplary cross-sectional view of a 3-D printed toolingshell 500 incorporating hollow structures and integrated channels. Thetooling shell may be composed of Invar, in whole or part, or of one ormore different materials, depending on the application for which thetooling shell is suited and on the composition of the panel to beproduced. Unlike conventional Invar tooling shells and other materialsthat are comparatively difficult to machine, the 3-D printed toolingshell 500 of FIG. 5 can be modeled to include any number of complexgeometries.

For example, the tooling shell 500 may comprise a plurality of hollowsections 508. These hollow sections 508 are, more fundamentally, definedvolumes of material vacancies within the tooling shell 500. Thesedefined volumes function to reduce an overall weight of the toolingshell 500 without sacrificing the amount of structural integrityrequired for the tooling shell 500 to be used in the molding process.While four hollow sections 508 are shown in this example, any number ofhollow sections, including a single hollow section disposedsubstantially along an axis of the tooling shell 500, may be used. Also,in lieu of hollow sections 508 disposed exclusively within the material,the hollow sections may also be formed as one or more indentations inthe material, such that at least one surface of the hollow section isexposed and such that the hollow section is not necessarily entirelywithin the tooling shell 500. Alternatively, the sections 508 may not beentirely empty but may, for maintenance of structural integrity or forother purposes, be filled with a substance that is substantially lighterthan the base material(s) used to create the tooling shell.

The use of hollow sections 508 is particularly advantageous in numerouscontexts. One context involves workers performing various stages of amanual molding process. Carrying the tooling shells and assembling themold becomes easier, especially where, as is commonplace, the basematerials from which the tooling shells are formed are otherwise heavyand impose burdens on the workers assembling and using the mold.

In another exemplary embodiment, the 3-D printed tooling shell 500comprises a plurality of integrated channels 502, 504, 506. Thesechannels constitute spaces within the tooling shell 500 that channelsubstances, gasses or heat to or from a surface 514 of the tooling shell500. In the example shown, channel 502 is used for resin infusion,channel 504 is used to create a vacuum between the tooling shells tofacilitate resin infusion from channel 502, and channel network 506 isused to maintain a temperature of a material by transferring heat to orfrom surface 514. Channel network 506 may also be used to provide highheat conditions to an area near surface 514 for heating the materials orcuring resin. Openings 510 are provided for each of the channels 502,504 and 506 to transfer the substances or heat to or from surface 514.Similarly, openings 512, shown at the lower surface 516 of the toolingshell 500, may be coupled to devices such as a resin injector, vacuumchamber, or temperature control unit. It will be appreciated that thenumber, geometry and functions of the channels 502, 504 and 506 can varydepending on the desired implementation. In addition, while openings 510and 512 are shown at the upper surface 514 and lower surface 516,respectively, of the 3-D printed tooling shell 500, the openings mayextend to different parts of the tooling shell 500. For example, one ormore of the openings 512 may be disposed on a side of the tooling shell.

Ordinarily, such complex geometries of tooling shell 500 would not bepractical for many materials suitable for molding. Further, manymanufacturers of composites lack the equipment necessary to cut andpolish metal tools such as Invar, so the services of a toolingspecialist may be required, adding to the manufacturers' cost. Further,Invar is one of the most expensive metallic tooling materials and,especially for large parts, the sheer size and weight of the tools makesthem difficult to handle. Additional parts including, for example, jigsand fixtures may be needed to add features to blocks of material duringa conventional machining process, making the conventional techniquesmore complex and time consuming. Accordingly, the use of 3-D printing torender a tooling shell having a streamlined, preconfigured geometry withhollow sections for lightweight handling and molding features includingintegrated channel structures may impart substantial cost savings andprovide significant benefits.

FIG. 6 is a flow diagram 600 illustrating an exemplary process forproducing a 3D-printed tooling shell incorporating hollow structures andintegrated channels. At 602, a 3-D printer receives instructions forprinting based on a data model as described in more detail above. Inaddition, at 604, the 3-D printer receives one or more materials for usein printing the tooling shell, such as the material(s) constituting thetooling shell. In some cases, the required materials may include supportmaterials for use in temporarily providing support to the structure bysupporting structure overhangs and providing a temporary fill for thevolumes of the hollow sections and/or channels to be formed.

At 606, the tooling shell is 3-D printed using any suitable printingtechnique. As part of the printing process 606, a sub-step 608 mayinvolve forming a plurality of channels disposed within the structurethat will be used for resin infusion, vacuum generation, or heattransfer. Similarly, a sub-step 610 may involve the formation of one ormore hollow sections to reduce an overall weight of the tooling shell,while not removing so much material as to compromise the tooling shell'soverall structural integrity to perform the task it is designed toperform.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these exemplary embodiments presented throughout thisdisclosure will be readily apparent to those skilled in the art, and theconcepts disclosed herein may be applied to other tooling shells andmethods of producing tooling shells. Thus, the claims are not intendedto be limited to the exemplary embodiments presented throughout thedisclosure, but are to be accorded the full scope consistent with thelanguage claims. All structural and functional equivalents to theelements of the exemplary embodiments described throughout thisdisclosure that are known or later come to be known to those of ordinaryskill in the art are intended to be encompassed by the claims. Moreover,nothing disclosed herein is intended to be dedicated to the publicregardless of whether such disclosure is explicitly recited in theclaims. No claim element is to be construed under the provisions of 35U.S.C. § 112(f), or analogous law in applicable jurisdictions, unlessthe element is expressly recited using the phrase “means for” or, in thecase of a method claim, the element is recited using the phrase “stepfor.”

What is claimed is:
 1. A method of three-dimensional (3-D) printing atooling shell, the method comprising: receiving instructions forprinting the tooling shell; melting or sintering a material comprising anickel alloy with a coefficient of thermal expansion (CTE) less than0.95 (×10⁻⁶° F.⁻¹) at 200 degrees Fahrenheit (° F.), such that thematerial is printed to form the tooling shell based on the instructions,the tooling shell consisting essentially of the nickel alloy.
 2. Themethod of claim 1, wherein the nickel alloy has a CTE of 0.72 (×10⁻⁶°F.⁻¹) at 200° F., 1.17 at 300° F., 2.32 at 500° F., and 4.22 at 700° F.3. The method of claim 1, wherein forming the tooling shell comprisesforming a channel in the tooling shell to enable resin infusion, vacuumgeneration, or heat transfer.
 4. The method of claim 3, wherein formingthe tooling shell further comprises forming a hollow section in thetooling shell.
 5. The method of claim 1, wherein forming the toolingshell comprises forming a hollow section in the tooling shell.
 6. Themethod of claim 1, further comprising: depositing, when the material ismelted, the melted material to form the tooling shell.
 7. The method ofclaim 1, wherein the sintering comprises selective laser sintering. 8.The method of claim 1, wherein the nickel alloy has a modulus ofelasticity of 20.5 megapound per square inch (Mpsi).
 9. The method ofclaim 1, wherein the nickel alloy comprises about 36% nickel and about64% iron.
 10. The method of claim 1, wherein forming the tooling shellcomprises forming one of a positive section or a negative section of thetooling shell.
 11. The method of claim 10, wherein the forming thetooling shell further comprises forming another of the positive sectionor the negative section of the tooling shell.